This adventure began atop Cannon Mountain in New Hampshire’s Franconia Notch. I managed to sneak away from a family visit long enough to take the aerial tramway to the summit in search of a very elusive bird.
Bicknell’s thrush is an alpine breeder. In the northeast, it nests in the stunted spruce zone at elevations between 3,000 and 4,200 feet.
Maine has suitable habitat on most of its taller mountains, but access is challenging on all of them.
Bicknell’s thrushes inhabit the stunted spruce because they can duck into the impenetrable scrub to elude predators. The harsh environment also discourages food competition from other bird species.
But high mountaintops remain a difficult place to live. Two alpine species, Bicknell’s thrush and blackpoll warbler, were added to Maine’s threatened species list just last year.
Cannon Mountain tops out at 4,080 feet. Not only is the stunted spruce zone easily reachable via the tramway, but a well-maintained summit path and an observation tower make it easy to explore.
Thousands of tourists visit every week, unaware that they are in the company of a rarely seen bird.
I was aware. I spotted my first Bicknell’s thrush on that same summit two decades ago. I’ve been up several times since, occasionally spotting another. They are notoriously difficult to see.
But not on this day. As I stood on a ledge, I was shocked when a thrush popped up next to me and started calling. From the next ledge, 100 yards away, another called. Within just a few minutes, I was easily seeing five notoriously sulky birds.
Then the singing started. They were clearly ignoring me and reacting to each other, though not in a belligerent way.
The Bicknell’s thrush has a reputation for singing only at dawn and dusk. But at 11 a.m., their songs were lilting all over the summit.
What explained this unusual day?
Unusual weather. I deliberately picked a perfect day — warm sun and low wind. All thrushes are enthusiastic singers. But on mountaintops, the wind typically comes up early and settles down late. Few birds sing into a stiff breeze, because they know they can’t be heard very far.
I think the dawn and dusk singing ritual among Bicknell’s thrushes has more to do with wind than any peculiar habit.
Their most unusual habit was on full display. These birds weren’t fighting over territory. They were advertising.
Bicknell’s thrush males and females both mate with multiple partners. Eggs in the nest typically have two or more fathers. Accordingly, fathers typically feed young in multiple nests. They don’t hold territories the way many birds do, and different males will sing from the same spot at different times without dispute.
It makes sense. In the poor visibility of thick vegetation, males would have difficulty enforcing fidelity anyway. And with such limited food supplies for hungry nestlings, cooperation beats competition.
Socialized hanky-panky in the bird world is unusual but not rare. In other low-visibility habitats such as grasslands and marshes, it is almost common.
Bobolinks spread their genes around multiple nests. In the same hayfields, male Savannah sparrows work a little harder to defend breeding territories, although enforcing fidelity is typically a losing battle.
In the marshes, red-winged blackbirds really mix things up. Males spend a tremendous amount of time declaring territories and warding off rivals. They use their red shoulders to display fierce aggression toward other males.
The blackbirds could learn a thing or two from Bicknell’s thrushes. Most of their territorial aggression is wasted energy. One male may have up to 15 nest-mates, yet up to half the eggs in his mates’ nests aren’t his.
Marsh wrens don’t fare much better. Both males and females aggressively defend their breeding territories. To ensure enough food for their kids, they will even destroy the eggs and nestlings of neighboring wrens. Normally, shared activities might strengthen a pair bond, but males regularly mate with other females.
It’s the same in salt marshes. Nelson’s sparrows and saltmarsh sparrows along Maine’s coast form parental pair bonds, but fidelity is iffy, at best. What happens in the marsh, stays in the marsh.
My mind is boggled by my recent encounter with the Bicknell’s thrushes.
I’ve seen these birds on four mountains in Maine, three in New Hampshire and one in Nova Scotia. Presumably, the same communal behavior I witnessed on Cannon Mountain happens on every mountain throughout their range.
But I’ve never seen this before, and I likely never will again.
